Field of the Invention
The present invention relates to a resist underlayer film composition for patterning by a multilayer resist process, a patterning process using the resist underlayer film composition, and a novel compound usable in the resist underlayer film composition.
Description of the Related Art
In recent years, problems of device operation failure due to an increase in gate leakage current arise with miniaturization and higher speed of transistors. Although a longer channel (a longer distance between a source and a drain) reduces the leakage current, this makes response speed lower and the transistor larger.
Fin-field effect transistor (Fin-FIT), which uses a three-dimensional gate, has been suggested to achieve conflict aims of miniaturization and a reduction in leakage current. The three-dimensional gate makes the channel long and enables the reduction in leakage current with miniaturization, higher speed, and lower power consumption. Fin-FIT was established based on a three-dimensional transistor shown in FIG. 2 of Patent Document 1. This great suggestion foresaw the problems decades ago and provided its solution.
Manufacture of the three-dimensional devices such as three-dimensional transistors uses substrates having concavity and convexity (three-dimensional device substrates), so that a top-down processing typified by lithography, which has been widely used for forming two-dimensional patterns, cannot be applied to the manufacture of the three-dimensional devices as it is used for forming two-dimensional patterns. Thus, a novel process and a material suited to the process have been desired for the manufacture of the three-dimensional transistors typified by Fin-FET.
The manufacture of the three-dimensional devices by lithography requires planarizing a photoresist film to cover a decrease in focus margin with miniaturization. On the other hand, the three-dimensional device substrates tend to have gaps with higher aspect ratio. To fill the gaps, a high technique for planarizing the photoresist film and the three-dimensional substrate has been required.
One example of such a method for manufacturing three-dimensional devices by lithography is a tri-layer (3-layer) process in which the gaps of the three-dimensional device substrate are planarized by an underlayer film (resist underlayer film) formed by spin coating, a silicon-containing middle layer film is formed thereon, and a photoresist film is formed thereon. In this method, the underlayer film needs excellent filling property.
Such manufacture of the three-dimensional devices by lithography requires forming a pattern with high aspect ratio by dry etching process. Thus, the underlayer film also needs high dry etching resistance, as well as filling property. Furthermore, the middle layer film on the underlayer film also needs high dry etching resistance, so that a metallic middle layer film formed by CVD or sputtering, which has higher dry etching resistance than a middle layer film formed by spin coating, is often selected as the middle layer film. Because the middle layer film usually requires 300° C. or higher temperature to be formed by CVD or sputtering, the underlayer film also needs high heat resistance to withstand this temperature.
A bisnaphtholfluorene novolak resin disclosed in Patent Document 2 is a high heat-resistant resin having a heat resistance of 500° C. Adding this bisnaphtholfluorene novolak resin and monomer components (bisnaphtholfluorene compounds) to an underlayer film composition enables the underlayer film composition to have increased flowability during baking at high temperature, thereby improving filling property. However, when the monomer components are added, outgas is generated in baking at high temperature and then adheres to a plate above a hot plate. This outgas can drop to the substrate and causes defects.
The generation of outgas can be prevented by crosslinking of the film. Thus, when a phenol compound, which has higher crosslinking rate and lower crosslinking temperature than a naphthol compound, is used in the underlayer film composition, the outgas generation is reduced compared with the case of using a naphthol compound. However, crosslinking reduces flowability of the underlayer film composition, so that if the phenol compound is used in the underlayer film composition, the underlayer film composition may crosslink at low temperature before flowing, thereby lowering filling property. Moreover, although filling property is generally improved by crosslinking at higher temperature, the phenol compound has low heat resistance disadvantageously.